1. Field of the Invention
The present invention is directed to alloys having useful application as coatings for gas turbine engine components and, more particularly, to coating alloys of the MCrAlY type having improved hot corrosion resistance.
2. Description of the Prior Art
Modern gas turbine engine superalloys are known to be susceptible to oxidation-corrosion over a range of elevated temperatures. As a result, it is the usual practice to coat the superalloys with a protective alloy which is compositionally different from and more oxidation-corrosion resistant than the superalloy substrate.
A type of coating alloy widely used in gas turbine engine applications, such as blades and vanes, is the so-called MCrAlY alloy where M is iron, nickel, cobalt and mixtures thereof. Various forms of the MCrAlY alloy are described in the patents to Talboom et al, U.S. Pat. Nos. 3,542,530; Evans et al, 3,676,085; Goward et al, 3,754,903 and Hecht et al, 3,928,026. Although these coating alloys have proved highly successful in gas turbine engine environments, efforts have continued to improve their corrosion resistance to sulfur and/or halide bearing compounds at elevated temperature, such as 1200.degree. F. to 1800.degree. F., and above. A result of this work is the platinum bearing MCrAlY coating alloy of Felton, U.S. Pat. No. 3,918,139, of common assignee herewith.